Matt Cassel has been around the NFL block a few times in his 10 seasons as a quarterback. Not much surprises him anymore, and yet he found himself unable to sleep the night before the Vikings minicamp this week.

“I was excited, jittery,” he said.

Chad Greenway felt those same butterflies. The veteran linebacker compared it to being a rookie or college freshman again.

“It was straight-up nerves,” he said.

Captain Munnerlyn arrived in town as a key offseason acquisition who’s supposed to help fix a shipwrecked defense, and even he felt a weird uneasiness.

“With a new coach, it’s a clean slate for everybody,” he said. “That means every position is open. Except for the running back position.”

Good call. We’ll go out on a limb and suggest that Adrian Peterson probably didn’t need to impress the new coaching staff in order to keep his job. But everyone else convened at Winter Park this week with an overarching sense of anxiety not normally evident at a routine offseason workout.

Imagine your first day with a new boss, one who’s known for his no-nonsense personality and brutal honesty. And salty language.

“You’re on edge and trying to make a good first impression,” Greenway said. “You know the draft is coming in a week. They’ll probably make some decisions based off of this camp.”

If Mike Zimmer’s first on-field introduction made players nervous and uncomfortable, that’s a good thing. This organization had become too lethargic under the previous regime. The atmosphere at Winter Park became stale as losses piled up last season.

Change can be refreshing that way. A new direction can reset the focus, create some positive energy and perhaps motivate anyone who treats his roster spot with a scholarship mentality.

Every coaching change in every sport generates initial platitudes about how a new attitude and higher expectations will produce better results. We heard those same things from Vikings players this week. It’s best not to get sucked into that trap without seeing some actual evidence.

Zimmer’s coaching style is dramatically different from Leslie Frazier’s, but that doesn’t necessarily mean one way is better than the other. But what’s indisputable is that this change has brought new accountability to the equation and forces each player to establish his own equity and trust with Zimmer’s staff.

“It’s almost like everybody is a new guy,” safety Harrison Smith said.

First impressions are tricky, but Zimmer’s reputation as a straight-shooter hits the mark. Asked an innocuous question about his open-door policy, Zimmer’s answer included this gem, “I’m not afraid of confrontation.” Then he quoted Pat Riley.

“Discipline is not a nasty word,” he said.

Two general observations resonated more than Zimmer’s bluntness. The confidence among the players in this staff’s competency is unmistakable, and Zimmer intends to take a hands-on approach in fixing his defense.

Frazier’s undoing rested largely on his choice of coordinators (in addition to his antiquated defensive scheme and willy-nilly mismanagement of the quarterback position). Alan Williams was overmatched, and Bill Musgrave’s offense often became more predictable than a low-budget horror film. Players lost confidence in both the plan and message.

It’s a safe bet that players won’t grumble about Zimmer’s aggressiveness on defense, and the size of Norv Turner’s playcard won’t become a punch line.

Veteran receiver Greg Jennings admitted the complexity of Turner’s offense makes his head spin. Peterson compared practices this week to “performing heart surgery without having a license.” Both were meant as compliments.

“What he says you can pretty much stamp it in concrete,” Jennings said.

Anyone remember players suggesting that of Musgrave? Or Williams?

Zimmer has ceded the offense to Turner, but it’s clear that the rookie head coach won’t just stand back and observe in silence, particularly with his defense. In minicamp workouts, he jumped into drills and barked at players about improper footwork or technique or whatever mistake caught his eye.

He’s more hands-on than a masseuse.

“You want to see a head coach coaching,” defensive end Brian Robison said.

Ultimately, Zimmer’s success will hinge on the organization’s ability to upgrade its talent — especially on defense — and solve a never-ending quarterback dilemma. And the onus falls squarely on the players, too. They can no longer blame the Tampa 2 for inept defense.

The players got their first glimpse of their new reality this week. The unknowns created some anxiety and put them on edge. That’s a good starting point.